Simplify the following expression: ${7(-3-z)-2(7z-7)}$
Explanation: Distribute the ${7}$ into the first set of parentheses: $ {7(}\gray{-3-z}{)} - 2(7z-7) $ $ {-21-7z} - 2(7z-7) $ Distribute the ${-2}$ into the parentheses: $ -21-7z {-2(}\gray{7z-7}{)} $ $ -21-7z {-14z+14} $ Rewrite the expression to group the ${z}$ terms and numeric terms: $ {-7z - 14z} {-21 + 14}$ Combine the ${z}$ terms: $ {-21z} {-21 + 14}$ Combine the numeric terms: $ {-21z} {-7}$ The simplified expression is $-21z-7$